1. Field of the Invention
The present invention relates to the cooling of electronic components. More specifically, the present invention relates to the cooling of a vertical monolithic circuit capable of conducting a one-way current entering or coming out through its rear surface.
2. Discussion of the Related Art
In monolithic electronic components or circuits, it is necessary to carry off the heat generated during operation. In particular, for semiconductor components with a junction, it is necessary to avoid changes in the temperature of the active junctions to guarantee stable operation characteristics.
FIG. 1 is a simplified cross-section view of a vertical electronic component 1 made in monolithic form in a semiconductor substrate, or vertical monolithic circuit. Component 1 comprises a metallization 5 on a rear surface. A current flows through the component from one or several metallizations (not shown) formed on the front surface towards rear surface metallization 5. To cool down the component, metallization 5 is thermally connected to an element for carrying off the heat or heat sink 7. Metallization 5 is generally electrically isolated from heat sink 7 by a thermally conductive element, generally a ceramic plate, a resin layer, or an isolating film 9.
The carrying off of the heat of heat sink 7 is performed by natural heat convection or by an airflow generated by a ventilator (not shown).
To improve the heat carrying-off, a heat pipe area of small dimensions, formed of an area comprising cavities in which a cooling fluid can flow, is sometimes formed in component 1.
In spite of this, for high-voltage one-way components such as diodes, transistors, or thyristors intended to operate at high powers on the order of several tens of watts or more, malfunctions can be observed. Such malfunctions are imputed to a drift in the characteristics (switching thresholds) as a result of a repeated heating of a component junction or area.
Further, Peltier coolers, which enable cooling heat sources, are known. Such coolers are, for example, formed of elementary cells comprising thermoelectric elements of two opposite conductivity types N and P.
FIG. 2 is a partial simplified cross-section view of the structure of a Peltier effect cell 10 on which is arranged a load to be cooled down.
Cell 10 comprises a first N-type doped thermoelectric element 11 and a second P-type doped thermoelectric element 12. First and second thermoelectric elements 11 and 12 are, for example, made of bismuth telluride (Bi2Te3). Element 11 is selenium-doped (type N) while element 12 is doped with antimony (type P). Elements 11 and 12 are electrically connected in series and thermally connected in parallel. For this purpose, elements 11 and 12 are laterally isolated, electrically and thermally. Their front surfaces are connected to a same conductive wafer 14. The rear surface of element 11 is integral with a metal plate 17 and the rear surface of element 12 is integral with a metal plate 18. Plate 17 is connected to a current input terminal A. Wafer 18 is connected to a current output terminal B. At its front surface, a thermally conductive and electrically isolating plate 20 forms a tray on which a load to be cooled down can be laid. At its rear surface, a thermally conductive and electrically isolating plate 22 thermally connects metallizations 17 and 18 to a heat sink 23.
In operation, a voltage such that cell 10 conducts a current entering through terminal A and coming out through terminal B, that is, running from N-type element 11 to P-type element 12, is applied between terminals A and B of cell 10. The current flow direction is indicated by arrows in FIG. 2. Then, plate 14 becomes a cold source at a temperature on the order of −10° C. for a current on the order of one ampere, while heat sink 23 becomes a hot source at a temperature from 30 to 50° C.
Peltier coolers seem extremely attractive and exhibit at first sight many advantages with respect to conventional heat dissipation systems but have not found many practical applications except, possibly, to cool down devices under confined or dangerous atmosphere. One of their disadvantages is that they require an autonomous current source capable of providing a high current.